These days I wondered why all of a sudden I could not control my PowerSDR mRX any more with CSVUserlistBrowser.
I had set up a virtual COM pair with com0com using COM5 on the PowerSDR side and COM6 with CSVUserlistBrowser.

The only thing I had changed in my PC was a plugged Huawei Mobile Connect stick for mobile phone internet access.
In the device manager it had created a port COM7 which seemed harmless.

But when I listed the COM ports I suddenly detected two ports COM6 in my PC! This should not have happened!
CSVUserlistBrowser (left) as well as PowerSDR mRX (right) listed two ports COM6. None of them could be opened and used.
The entry ACMSerial_1 by no doubt belonged to the Huawei Mobile Connect stick. When I removed the stick, ACMSerial_1 disapperared,
but unfortunately com0com COM6 disapperared as well!

As I found no way to re-configure this port 6 for the Huawei stick I was forced to use
another COM pair of com0com for communication between PowerSDR and CSVUserlistBrowser (COM12/COM13).

If you should have trouble with COM ports: Look if you have two COM ports in your system with identical names! In my case the fault
is clearly with the Huawei Mobile Connect driver. It should not have created a COM6 as this port already belonged to com0com and was in use!